The subject of the present invention is a device for respiratory assistance which can be used on patients in whom spontaneous respiration is absent or inadequate, whether or not said patients are placed under artificial respiration.
Various devices are known, such as masks and oral, nasal, endotracheal and tracheotomy probes or cannulas, which are intended to form the junction between an artificial respiration and/or anesthesia apparatus and the respiratory system of a patient. These devices, essentially in the form of tubes, can, depending on the circumstances, include immobilizing means such as flanges or collars in the vicinity of the proximal end for holding them on the mouth or nose of the patient, or alternatively inflatable balloons in the vicinity of the distal end for holding them by friction in the trachea.
The known devices have significant disadvantages. Thus, for example, when a tube of a known type is disconnected from the artificial respirator and the patient needs oxygen-enriched air, it is necessary to introduce into said tube a probe which is connected to an oxygen source. Moreover, in cases of inadequate spontaneous respiration, the patient must necessarily remain connected to the respirator until spontaneous respiration has been completely re-established.
Thus to overcome these disadvantages, it has already been proposed, for example in document EP-A-0 390 684, to provide devices for respiratory assistance which, in addition to the main channel formed by the tube, comprise at least one auxiliary channel, for example formed in the wall of said tube, permitting injection of a jet of respirable gas (oxygen, air or air/oxygen mixture) intended to ventilate the patient, these auxiliary channels opening into the main channel in the vicinity of the distal end of the latter.
To prevent the jets of respirable gas from striking directly against the mucosa of the patient under ventilation, the kinetic energy of these jets risking trauma to said mucosa, it is provided, in these latter devices, that at least the distal end of said auxiliary channels opening into the main channel is parallel to the latter and, opposite the distal orifice of each auxiliary channel, there are means for deflecting said jets of respirable ventilation gas toward the inside of said main channel.
Thus, the jets of respirable gas passing through said auxiliary channels are deflected toward the axis of the main channel when they penetrate into the latter. Experimental measures have shown that downstream of said means of deflection, inside said main channel, a pressure zone of oblong shape is formed starting at the outlets of said auxiliary channels into the main channel and extending in the axial direction along the axis of said main channel, with gradual reduction of its cross section, so as to occupy only In the central part thereof, while downstream of said high pressure zone, the pressure of said jets of respirable gas falls and the jets of gas emerge at low pressure through the distal orifice of the tube. Experience has also shown that downstream of the distal outlet of the tube, the pressure is low and is maintained constant throughout the entire respiratory space. This pressure is dependent on the flow rate of respirable gas in the auxiliary channels. Consequently, with the respiratory assistance device according to the above document, it is possible for example to deliver oxygen or an air/oxygen mixture directly into a patient""s lungs, at the level of the carina, and thus suppress the dead space which exists in the other known probes and which is about one third of the total respiratory volume for an adult and about half for premature babies. Suppression of this dead space corresponds to an increase in performance of the respiratory cycle of more than 25% in all patient cases and of nearly 50% in certain cases.
The device in document EP-A-0 390 684 is thus particularly advantageous. However, it has the disadvantage of requiring a source of respirable gas at high pressure (several bar) to supply said auxiliary channels. Such a source may not be available and it may be expedient, for reasons of safety, to be able to use sources of respirable gas at low pressure (for example below one bar).
Thus, the object of the present invention is to improve the device in document EP-A-0 390 684 so that it can function with a source of respirable gas at low pressure.
To this end, according to the invention, the device for respiratory assistance comprising a tube which forms a main channel and which is intended to be connected via its distal end to the respiratory tract of a patient so that said main channel connects the respiratory system of said patient to the outside, said device moreover comprising at least one auxiliary channel connected at its proximal end to a source of respirable gas so as to insufflate a jet of such a respirable gas into said respiratory system, and whose distal end opens into said main channel in the vicinity of the distal end of the latter, means for deflecting said jet of respirable ventilation gas in the direction of the inside of said main channel being provided opposite the distal orifice of said auxiliary channel so that, downstream of said means of deflection, inside said main channel, a pressure zone of oblong shape is formed starting at said distal orifice and extending in the distal direction along the axis of said main channel, with gradual reduction of its cross section as it moves away from the inner wall of said main channel so as to occupy only the central part of the latter, is distinguished by the fact that it comprises a ring arranged in said main channel downstream of said means of deflection (in relation to said jet of respirable gas), and by the fact that said ring encloses said oblong pressure zone by at least partially closing off the peripheral space of said main channel situated between said inner wall thereof and said oblong pressure zone.
The Applicant found that by means of this ring it was possible to use a source of respirable gas at lower pressure while obtaining an oblong pressure zone of identical pressure, or alternatively to obtain an oblong pressure zone at higher pressure using a source of respirable gas of identical pressure. It was therefore as if said ring, by peripherally restricting said main channel and leaving only the central part of the cross section thereof free, permitted better utilization of the pressure of said source of respirable gas for forming said oblong pressure zone.
The Applicant found by experimentation that it was advantageous for the distance separating said ring from said means of deflection to be approximately equal to the diameter of the distal part of said main channel. Said ring could be fixed inside said main channel or even form an integral part of said tube. However, in order to be able to optimize the pressure gain on the source of respirable gas, it is preferable for this distance to be adjustable. For the same purpose, it is also advantageous for the internal diameter of said ring to be adjustable in order to adapt the orifice of the latter to the central section of said pressure zone to the best possible extent. It is then expedient to provide a set of interchangeable rings, of different internal diameters, which can be introduced and displaced by sliding inside the distal end of said tube. Alternatively, it is possible to use rings in the form of inflatable cuffs in such a way as to be able easily to modify their internal diameter.
It will also be noted that by virtue of the present invention it is particularly easy to provide a humidifier in the conduit connecting the source of respirable gas to the auxiliary channel. Indeed, the present invention makes it possible to lower the pressure of the jet of respirable gas in said conduit to a level permitting good humidification thereof. It is thus possible to prevent the patient""s mucosa from drying out.
When the device according to the invention advantageously includes a plurality of auxiliary channels, it is advantageous for at least some of them to be supplied jointly with respirable gas. Such joint supply of said channels can be achieved by way of a distribution ring which is coaxial with said tube. Moreover, said auxiliary channels which are not jointly supplied can be used for introducing additional gaseous products such as medicinal products.
Thus, it will be seen that the device according to the invention permits, in complete safety:
humidification of the insufflated respirable gas,
long-term intubation of the respiratory assistance without drying,
injection of medicines or anesthetics during respiratory assistance,
dynamic measurement of pressures, since it suffices to provide auxiliary channels to which appropriate probes are associated,
establishment of a microflow of respirable gas in the auxiliary channels to prevent obstruction of said channels by mucus,
an increase in the volume exchanged, since the pressure is automatically limited and there is no risk of crushing of the pulmonary capillaries,
for the same quantity of oxygen exchanged, a decrease in the amount of oxygen in the mixture, which accordingly reduces the secondary effects of the assistance,
the possibility of using respirators which are less expensive then the current respirators.
It is also advantageous, particularly for safety reasons, for the device according to the present invention to have a controllable valve mounted in the conduit connecting the source of respirable gas to said auxiliary channel and for said valve to be controlled by a sensor detecting the patient""s exhalation. Thus, said valve can be closed during the patient""s exhalation, so that this exhalation is free through said tube, the jets of respirable gas and said central oblong pressure zone then being suppressed. Said sensor preferably detects the patient""s exhalation downstream of said ring, that is to say in the direction away from said means of deflection.